Mobile communication devices are increasing popular for communication and other tasks. As their functionality has increased, the need for additional surface area on which larger displays, finger friendly keypads, as well as the placement of camera apertures, speaker ports, battery charger jacks, and communication cable jacks can be placed on the device has also increased. This has created challenges in meeting the demand for increasingly smaller devices. To maximize surface area, a common design chonfiguration in cellular telephones, for example, is a device having two housings that are connected by a coupling mechanism, which enables the two parts to move relative to one another. The first housing will often include the keypad, the battery, the microphone, and much of the control circuitry of the telephone including various hardware and software elements. The second housing for example can include one or more display elements, speaker ports, as well as other supporting circuitry.
There are many different ways to configure a cellular telephone having two housings. For example, a hinge and/or a rotatable coupling between the two housings may be used for a “clamshell” model or a “rotator” model. Alternatively, the second housing may slide over the first housing to open the device. In a “slide” configuration, the two housings may be connected together without the use of a hinge. In the clamshell model, the second housing traditionally folds closed over the first housing when the telephone is not in use.
In clamshell phones, the second housing or the flip usually contains the earpiece or speaker, and two displays, one on either side of the second housing. The first housing or base usually contains the keypad and a lion's share of the hardware and software components. Most clamshell phones have a feature called “active flip,” with which calls can be answered and ended through a detection of the opening and closing of the telephone (i.e. the two part housing).
Of course, there are more dual (first and second) housing configurations than those discussed here. The common feature of the different dual housing configurations is that they are connected by an appropriate type of housing connector mechanism. Because active elements are often placed in the flip portion of the housing away from the main control and power circuitry, which are typically located within the base portion of the housing, wires extend from the first housing (i.e. base) to the second housing (i.e. flip) through the housing coupling mechanism to support the functions of the features located in the second housing.
When a second housing includes two displays, the first display typically is viewable when the device is open, and a second display typically is viewable when the device is closed. Commonly the displays will project different information, which generally requires different data signals to be generated for driving each of the first and second display. Furthermore differences in the size and the display capabilities may result in more or less data needing to be sent for purposes of projecting the desired information. For example, the first display may be a full screen display located in the second housing. The second display in the second housing may be a smaller caller line identification (CLI) display. Oftentimes, the CLI may include more than just caller ID data. It may also include time and date, plus potentially other information.
A substantial number of the display apparatus' processing components are housed in the first housing. Leads from the first housing for both display devices are threaded through the housing connector mechanism to the second housing. For example, the lines can include those for power, ground, and control and I/O signal lines. There may be, for example, eight lines for eight bit or sixteen lines for sixteen bit parallel communication with a CPU, with numerous additional lines. In order to support more than one display, more than one set of lines may generally be involved, which together can include dozens of lines.
While there is a trend toward smaller cellular telephone devices, there is also a trend toward more features and higher capability for the current features. Fewer and smaller hardware and software components are therefore desirable to enable a higher number of features and to improve the current features in the smaller devices (i.e. do more with less). Accordingly, it may be beneficial to eliminate a portion or all of one set of leads that supports one of the displays.
Communication of data to the display devices, in general, can be a significant source of power consumption in devices. With more and better features in the new smaller devices creating additional drain on power resources, it would be further beneficial if the power needs for the communication of data to the one or more displays were reduced.